What Happens When Pipes Burst?
When water freezes, it expands in volume by about nine percent. That doesn’t sound like much, but inside a sealed pipe, it’s enormous.
As ice forms inside the pipe, pressure builds. The pressure inside the line can jump from a normal 40 pounds per square inch (psi) to as much as 40,000 psi. No pipe — copper, PEX, galvanized, or PVC — is designed to handle that. Eventually, something has to give, and the pipe splits, cracks, or bursts.
Important detail: the actual break doesn’t always happen where the ice is. Often, the ice plugs one section, and the expanding pressure pushes on liquid water further down the line. The pipe then bursts at a weak spot inches or even feet away from the frozen area.
Once the ice begins to thaw and water starts flowing again, a burst pipe can send a torrent of water into your home, flooding basements, soaking ceilings, and damaging walls, insulation, and flooring. Beyond the obvious mess and structural damage, trapped moisture can also lead to hidden mold growth — a slower, more expensive problem down the road.
Pipes at highest risk include:
- Pipes running through unheated spaces (garages, crawl spaces, basements, attics).
- Pipes located in exterior walls with poor or missing insulation.
- Any pipes directly exposed to the elements: hose bibs, sprinkler lines, evaporative cooler supply lines, and outdoor plumbing.
The key is simple: keep pipes warm enough so the water inside never reaches freezing — or give the system safe ways to relieve pressure during extreme cold.
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